The strength of soil–industrial by-products–lime blends

The aim of this study is to assess the strength controlling parameters of a sandy soil (Botucatu residual soil (BRS)) treated with industrial by-products (basaltic powdered rock (PR) or coal fly ash (FA)) and lime, as well as to show that the porosity/volumetric lime content (η/L_v) plays a fundamental role in the assessment of the target strength. The controlling parameters evaluated were addition of industrial wastes, quantity of lime, porosity and η/L_v. The unconfined compressive strength (q_u) increased non-linearly with the amount of lime and decreased with porosity for all studied mixtures. Similar equations were found relating q_u to η/(L_v)^0·12 for BRS–lime, BRS-PR–lime and BRS-FA–lime mixtures. Tests of potential reactivity of siliceous materials with alkalis on the materials studied indicated that the higher amount of dissolved silica in the alkaline environment of the FA, when compared with the BRS and the PR, was responsible for increasing the number of reactions with the lime and consequently increasing the strength for BRS (25% FA)–lime mixtures, when compared to BRS–lime and BRS (25% PR)–lime blends.